Tyrosyl Phosphorylation of Shp2 Is Required for Normal ERK Activation in Response to Some, but Not All, Growth Factors

摘要: The protein-tyrosine phosphatase Shp2 is required for normal activation of the ERK mitogen-activated protein kinase in multiple receptor tyrosine signaling pathways. In fibroblasts, undergoes phosphorylation at two C-terminal tyrosyl residues response to some (fibroblast growth factor and platelet-derived (PDGF)) but not all (epidermal insulin-like factor) factors. Whereas catalytic activity actions, effect on function has been controversial. To clarify role phosphorylation, we infected Shp2-mutant fibroblasts with retroviruses expressing wild type or mutants either (Y542F Y580F) both (Y542F,Y580F) tyrosines. Compared cells, was decreased Y542F- Y580F-infected cells fibroblast PDGF epidermal factor. Mutation sites resulted a further decrease factor-evoked activation, although level vector control. Immunoblot analyses confirm that Tyr-542 Tyr-580 are major Grb2 binding site. However, studies antibodies specific individual reveal unexpected complexity mechanism by different kinases. Moreover, because Y580F retain nearly Grb2-binding ability, yet exhibit defective PDGF-evoked our results show association sufficient promoting full these factors, thereby arguing strongly against "Grb2-adapter" model action.